The current V8 5 series use recirculating ball steering for two reasons: 1)They couldn't fit rack and pinion gear in the engine compartment due to the size of the V8 engine blocks 2)RB steering provides more smoother handling and feel over a variety of road surfaces whereas R&P provides outstanding input and feedback control but does tend to transfer more road harshness to the wheel. For the M5, they added Servotronic with additional control of the RB mechanism to eliminate as much of the "dead on center" phenomenon common with RB steering.